U.S. patent application number 12/218064 was filed with the patent office on 2009-01-15 for apparatus and method for inspecting liquid crystal display.
Invention is credited to Han Rok Chung.
Application Number | 20090015825 12/218064 |
Document ID | / |
Family ID | 40252827 |
Filed Date | 2009-01-15 |
United States Patent
Application |
20090015825 |
Kind Code |
A1 |
Chung; Han Rok |
January 15, 2009 |
Apparatus and method for inspecting liquid crystal display
Abstract
A method of inspecting a liquid crystal display panel includes
providing a liquid crystal display panel to be inspected, turning
on a backlight unit that is disposed under the liquid crystal
display panel to emit light toward the liquid crystal panel,
driving the liquid crystal display panel by applying test signals
to the liquid crystal display panel on a predetermined period,
detecting defects by taking an image of the liquid crystal display
panel on a period shorter than the driving period of the liquid
crystal display panel, and detecting defects created in the liquid
crystal display panel, which blink in accordance with a period of
the test signals of the liquid crystal display panel.
Inventors: |
Chung; Han Rok; (Dalseo-gu,
KR) |
Correspondence
Address: |
MCKENNA LONG & ALDRIDGE LLP
1900 K STREET, NW
WASHINGTON
DC
20006
US
|
Family ID: |
40252827 |
Appl. No.: |
12/218064 |
Filed: |
July 11, 2008 |
Current U.S.
Class: |
356/239.2 |
Current CPC
Class: |
G01N 2021/9513 20130101;
G01N 21/95 20130101 |
Class at
Publication: |
356/239.2 |
International
Class: |
G01N 21/88 20060101
G01N021/88 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 11, 2007 |
KR |
10-2007-0069858 |
Claims
1. A method of inspecting a liquid crystal display panel,
comprising: providing a liquid crystal display panel to be
inspected; turning on a backlight unit that is disposed under the
liquid crystal display panel to emit light toward the liquid
crystal display panel; driving the liquid crystal display panel by
applying test signals to the liquid crystal display panel at a
predetermined period; detecting defects by taking an image of the
liquid crystal display panel on a period shorter than the driving
period of the liquid crystal display panel; and detecting defects
created in the liquid crystal panel, which blink in accordance with
a period of the test signals of the liquid crystal display
panel.
2. The method according to claim 1, wherein the turning-on period
is greater than the driving period of the liquid crystal display
panel.
3. The method according to claim 1, wherein the detecting of the
defects by taking the image includes defecting all defects
generated at an inside and an outside of the liquid crystal display
panel and on the upper and lower polarizing plates.
4. The method according to claim 3, wherein the defects at the
inside and outside of the liquid crystal display panel and on the
upper and lower polarizing plates are detected in a white
state.
5. The method according to claim 1, wherein the driving period of
the liquid crystal display panel is 30 msec and repeats an on/off
switching in a vertical or horizontal direction.
6. The method according to claim 1, further comprising turning on
side light generating units disposed at both sides of the liquid
crystal display panel when the backlight unit is turned on.
7. An apparatus for inspecting a liquid crystal display panel,
comprising: a camera disposed above a liquid crystal display panel;
a backlight unit disposed under the liquid crystal display panel; a
driving unit for driving the camera, liquid crystal display panel,
and backlight unit; and an inspecting unit for storing defect
information taken by the camera.
8. The apparatus according to claim 7, further comprising side
light generating units disposed at both sides of the liquid crystal
display panel.
9. The apparatus according to claim 7, wherein the defect
information stored in the inspecting unit includes location and
number information of real defects generated inside the liquid
crystal display panel and location and number information of defect
generated outside the liquid crystal display panel.
10. The apparatus according to claim 7, wherein the driving unit
drives the backlight unit, the liquid crystal display panel, and
the camera by making a turning-on period of the backlight unit, a
driving period of the liquid crystal display panel, and an image
taking period of the camera different from each other.
Description
[0001] The present application claims priority under 35 U.S.C. 119
and 35 U.S.C. 365 to Korean Patent Application No. 10-2007-0069858,
filed on Jul. 11, 2007, which is hereby incorporated by reference
for all purposes as if fully set forth herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an apparatus and method for
inspecting a liquid crystal display.
[0004] 2. Discussion of the Related Art
[0005] As the information-oriented society has arrived, a
requirement for flat panel displays that are light and thin and
have lower power consumption is on the rise.
[0006] Among the flat panel displays, liquid crystal displays have
been widely used for laptop computers and desktop computers.
[0007] Generally, a liquid crystal display includes two substrates
facing each other, electric field generating electrodes formed on
inner surfaces of the substrates, and a liquid crystal material
injected in a space defined between the substrates. When a voltage
is applied to the electrodes, liquid crystal molecules are twisted
by an electric field to vary transmittance of the light, by which
an image is displayed.
[0008] In the related art, many inspection processes are performed
in the course of manufacturing the liquid crystal display.
Particularly, after an array substrate is made, an array test
process is performed to check for a pixel defect and a line cut,
and the like. After the array substrate is attached to a color
filter substrate, a lightening test for the liquid crystal panel is
performed in a cell process.
[0009] In the cell process, an auto-probe device is used to allow a
proof pin to contact the liquid crystal panel, after which a tester
checks for the defect of the liquid crystal panel through a test
using an optical device and his/her eyes in a state where the
liquid crystal panel is driven.
[0010] That is, after the test signal is applied to the liquid
crystal panel in the auto-probe device, a light source of a
backlight is variously turned on to inspect a point defect and a
line defect of the liquid crystal panel.
[0011] However, the test method of the related art has the
following limitations.
[0012] First, as the liquid crystal display is enlarged above 40
inches, the test using the tester's eyes has a limitation.
[0013] Second, since the point and line defects of the liquid
crystal panel are performed by the tester, after selecting defect
candidates in advance, determining pass or fail by precisely
inspecting the liquid crystal panel, it takes long time to perform
the test.
[0014] Third, for the point defect, it is difficult to discriminate
between a foreign substance on an outer surface of the liquid
crystal panel or a polarizing panel and a foreign substance on an
inner surface of the liquid crystal panel.
[0015] Particularly, the point defect caused by the foreign
substance on the inner surface of the liquid crystal panel is a
real defect that is directly related to the defect of the liquid
crystal panel. Therefore, an accurate inspection for the point
defect is required. However, the inspection method of the related
art cannot perform the accurate inspection.
SUMMARY OF THE INVENTION
[0016] Accordingly, the present invention is directed to an
apparatus and method for inspecting liquid crystal display that
substantially obviate one or more of the problems due to
limitations and disadvantages of the related art.
[0017] An advantage of the present invention is to provide an
apparatus and method of inspecting a liquid crystal display, which
can accurately inspect a foreign substance generated inside a
liquid crystal panel by adjusting an image capturing speed of a
camera and a driving interval of the liquid crystal panel.
[0018] Additional features and advantages will be set forth in the
description which follows, and in part will be apparent from the
description, or may be learned by practice of the invention. The
objectives and other advantages of the invention will be realized
and attained by the structure particularly pointed out in the
written description and claims hereof as well as the appended
drawings.
[0019] To achieve these and other advantages and in accordance with
the purposes of the present invention, a method of inspecting a
liquid crystal display includes providing a liquid crystal panel to
be inspected, turning on a backlight unit that is disposed under
the liquid crystal panel to emit light toward the liquid crystal
panel, driving the liquid crystal panel by applying test signals to
the liquid crystal panel on a predetermined panel, detecting
defects by taking an image of the liquid crystal panel on a period
shorter than the driving period of the liquid crystal panel, and
detecting defects created in the liquid crystal panel, which blink
in accordance with a period of the test signal of the liquid
crystal panel.
[0020] In another aspect of the present invention, an apparatus for
inspecting a liquid crystal display includes a camera disposed
above a liquid crystal panel, a backlight unit disposed under the
liquid crystal panel, a driving unit for driving the camera, liquid
crystal panel, and backlight unit, and an inspecting unit for
storing defect information taken by the camera.
[0021] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory, and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this application, illustrate embodiments of
the invention and together with the description serve to explain
the principle of the invention.
[0023] In the drawings:
[0024] FIG. 1 is a schematic view of an apparatus for inspecting a
liquid crystal display according to an embodiment.
[0025] FIGS. 2A and 2B are views illustrating a method of
inspecting a liquid crystal display using a camera of an inspection
apparatus according to an embodiment.
[0026] FIG. 3 is a view illustrating a liquid crystal display
inspection process according to an embodiment.
[0027] FIGS. 4A and 4B are views illustrating an inspection process
for a real defect generated inside a liquid crystal panel according
to an embodiment.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0028] Reference will now be made in detail to embodiments of the
present invention, examples of which are illustrated in the
accompanying drawings.
[0029] FIG. 1 is a schematic view of an apparatus for inspecting a
liquid crystal display according to an embodiment.
[0030] As shown in FIG. 1, a liquid crystal display includes a
liquid crystal display panel 40, upper and lower polarizing plates
35a and 35b disposed on top and bottom surfaces of the liquid
crystal display panel 40, and a backlight unit 10 disposed under
the lower polarizing plate 35b. A camera 30 for inspecting foreign
substances on the upper and lower polarizing plates 35a and 35b and
a point or line defect of the liquid crystal display 40 is disposed
above the upper polarizing plate 35a. Side light generating units
20 are disposed at left and right sides of the liquid crystal panel
40. A control system 50 is provided to control the defect
inspection.
[0031] The control system 50 includes a driving unit 70 for
selectively or wholly driving the camera 30, side light generation
unit 20, liquid crystal display panel 40, and backlight unit 10 and
an inspecting unit 60 for storing and reading defect information
taken by the camera 30.
[0032] Here, the liquid crystal display panel 40 includes an array
substrate on which a plurality of gate lines extending in a
direction and spaced apart from each other, and a plurality of data
lines extending a direction perpendicular to the gate lines, a
plurality of thin film transistors formed at matrix pixel regions
defined by the gate and data lines, and a plurality of pixel
electrodes, a color filter substrate having a black matrix and a
color filter layer, and a liquid crystal layer disposed between the
array and color filter substrates that are attached to each
other.
[0033] The camera 30 is disposed above the liquid crystal display
panel 40 and is capable of moving upward, downward, leftward, and
rightward. That is, the camera 30 takes an image while scanning in
a horizontal direction and moving in a vertical direction.
[0034] The following will describe an apparatus and method for
inspecting the liquid crystal display panel according to an
embodiment.
[0035] First, point and line defects for an entire region of the
liquid crystal display panel 40 are inspected by the turning on/off
of the backlight unit 10 and operation of the liquid crystal panel
40 and camera 30. At this point, the backlight unit 10 is turned on
and off by the driving unit 70 of the control system 50. The liquid
crystal display panel 40 is also driven in accordance with test
signals red, green, and blue signals applied from the driving unit
70. Therefore, the light generated by the backlight unit 10 is
polarized while passing through the lower polarizing plate 35b and
subsequently passes through the liquid crystal display panel 40.
The light travels to the upper polarizing plate 35a to realize a
desired test image.
[0036] At this point, the camera 30 takes a front image of the
liquid crystal display panel 40 or takes an entire region of the
liquid crystal display panel 40 while scanning in a predetermined
direction to detect the locations and number of defects. When the
defects are detected, the defect information is stored in an
inspection unit 60 of the control system 50.
[0037] Therefore, point defects of the defect information stored in
the inspection unit 60 include all defects formed inside and
outside of the liquid crystal display panel 40 and on the upper and
lower polarizing plates 35a and 35b.
[0038] After the above, the driving unit 70 of the control system
50 turns on and off the side light generating unit 20 and inspects
for foreign substances generated on the surface of the liquid
crystal display panel 40 or the surface of the upper polarizing
plate 35a.
[0039] The defects detected by the driving of the side light
generating unit 20 include defects generated on the surface of the
liquid crystal display panel 40 or the surface of the lower
polarizing plate 35b.
[0040] As described above, when the defect inspection by the side
light generating unit 20 is completed, a real defect inspection is
performed by the liquid crystal display panel 40 and the adjustment
of an image take speed (image take period) of the camera 30. The
real defects include foreign substance defects generated at the
pixel regions on the inner surface of the surfaces facing each
other or between the liquid crystal layer and the substrates.
[0041] In the real defect inspection method, the backlight unit 10
is periodically turned on and off and the liquid crystal display
panel 40 is driven on a period shorter than the turning-on period
of the backlight unit 10 (e.g., on a period half the turning-on
period of the backlight unit 10. In addition, the image take speed
of the camera 30 is set to be shorter than the driving period of
the liquid crystal display panel 40 (e.g., 1/4 of the backlight
turning-on period). At this point, the side light generating unit
20 may be driven or not
[0042] Thus, since the turning-on period of the backlight unit 10
is longest, it is recognized that the backlight unit 10 is always
in the on-state on the camera's part and the liquid crystal display
panel's part. Since the liquid crystal display panel 40 is turned
on/off by at least one time during the on-state of the backlight
unit 10, defects existing inside the liquid crystal display panel
40 are detected in a blinking state.
[0043] That is, defects are detected in a white or black color in
accordance with the twisting or the non-twisting of liquid crystal
molecules in the liquid crystal panel 40.
[0044] Since the camera 30 takes successively the images at a speed
faster than the driving period of the liquid crystal display panel
40, it can detect bright points and dark points generated by the
defects inside the liquid crystal display panel 40.
[0045] That is, the image take speed of the camera 30 is much
faster than the driving speed (on/off of liquid crystal molecules)
of the liquid crystal display panel 40, the camera 30 can detect
all of the states that are varied depending on the operation of the
liquid crystal display panel 40.
[0046] Therefore, in the embodiment, all of the foreign substance
defects are inspected by the operation of the backlight 10 and the
camera 30 (the number of the defects is "m") and the foreign
substance defects on the polarizing plate and an outer surface of
the liquid crystal display panel are inspected by the operation of
the side light generating unit 20 (the number of defects is "n").
The number of real defects generated inside the liquid crystal
display panel 40 can be accurately detected using a different
between the defect numbers (m-n).
[0047] In addition, in the embodiment, by adjusting the image take
speed of the camera 30, the driving time of the liquid crystal
display panel 40, and the turning-on time of backlight unit 10, the
defects generated inside the liquid crystal display panel 40
periodically blink and thus the real defects can be accurately
inspected.
[0048] FIGS. 2A and 2B are views illustrating a method of
inspecting a liquid crystal panel display using a camera of an
inspection apparatus according to an embodiment. FIG. 2A
illustrates a method for inspecting an entire region of liquid
crystal display panel by scanning the liquid crystal panel in a
substantially horizontal direction at an upper portion and moving
the camera in a substantially perpendicular direction. FIG. 2B
illustrates a method for inspecting the entire region of the liquid
crystal display panel by disposing the camera above the liquid
crystal display panel such that the entire region of the liquid
crystal display panel can be included in an image taking range of
the camera.
[0049] A light intensity adjustor may be attached on the camera of
the inspection apparatus. By the light intensity adjustor, a
standard by which the defect is determined can be adjusted in
accordance with a luminance of scattered light.
[0050] FIG. 3 is a view illustrating a liquid crystal display panel
inspection process according to an embodiment.
[0051] Since the liquid crystal display panel inspecting apparatus
is as that of FIG. 1, like reference numbers will be used to refer
to like parts.
[0052] As shown in FIG. 3, the backlight unit 10 is turned on and
the red, green, and blue signals (test signals) for inspecting the
liquid crystal display panel 40 are applied. Subsequently, defects
are detected using the method described in FIGS. 2A and 2B.
[0053] Therefore, the camera 30 detects defects A inside the liquid
crystal panel 40, defects B outside the liquid crystal panel 40,
and defects C on the upper and lower polarizing plates 35a and 35b.
Information on the location and number of the detected defects is
stored in the inspection unit 60 of the control system 50.
[0054] Next, by driving the side light generating unit 20, the
outside defect B of the liquid crystal display panel 40 and the
defects C on the upper and lower polarizing plates 35a and 35b are
detected. The information on the detected defects is stored in the
inspection unit 60 of the control system 50.
[0055] After the above, real defects A inside the liquid crystal
display panel 40 are extracted by subtracting the defects detected
by the side light generating unit 20 from all of the defects.
[0056] Here, the real defects A are defects generated inside the
liquid crystal display panel 40, which cannot be removed through a
simple cleaning process. Therefore, it is important to identify the
accurate locations of the real defects A.
[0057] FIGS. 4A and 4B are views illustrating an inspection process
for a real defect generated inside a liquid crystal display panel
according to an embodiment.
[0058] As shown in FIGS. 4A and 4B, by making the turning-on period
of the backlight unit 10 longer than the driving period of the
liquid crystal panel 40 and the image taking period of the camera
30, the backlight unit 10 maintains the turning-on state when the
liquid crystal display panel 40 is driven and the camera 40 takes
an image.
[0059] Next, by making the image taking speed (image taking period)
of the camera shorter than the driving period of the liquid crystal
display panel 40, the defects A generated inside the liquid crystal
display panel 40 are detected. For example, when the driving pulse
period of the liquid crystal display panel 40 is 30 msec, the image
taking speed of the camera 30 is set to have 5-30 msec shorter than
30 msec.
[0060] In addition, test signals applied to the liquid crystal
display panel 40 are switching signals that turn on/off in a
vertical direction (TN mode) or in a horizontal direction (IPS
mode).
[0061] When the driving period of the backlight unit 10, the
driving period of the liquid crystal display panel 40, and the
image taking period of the camera 30 as described above, the
backlight unit 10 maintains the turning-on state when the liquid
crystal display panel 40 and the camera 30 operate and thus the
defects A, B, and C are detected by the camera 30 as they are in a
white state. At this point, the side light generating unit 20 may
be in an on-state or an off-state.
[0062] Since the image taking speed of the camera 30 is much faster
than the driving periods of the backlight unit 10 and liquid
crystal display panel 40, all of the defects A, B, and C can be
primarily detected. Particularly, since the on/off signals are
applied to the liquid crystal display panel 40, the defects B
existing in the liquid crystal display panel 40 are detected as
they blink.
[0063] As shown in the drawings, when the off signal is applied to
the liquid crystal display panel 40, the liquid crystal molecules
in the liquid crystal display panel 40 intercept light from the
backlight unit 10 and thus the light is detected by the camera 30
as they are in a black state.
[0064] Therefore, by simply adjusting the turning-on period of the
backlight unit 10, the driving period of the liquid crystal display
panel 40, and the image taking period of the camera 30, real
defects A existing in the liquid crystal panel 40 and foreign
substance defects existing on the upper and lower polarizing plates
35a and 35b and on the outside of the liquid crystal display panel
40 can be detected.
[0065] As described above, by adjusting the driving period of the
liquid crystal display panel 40 and the image taking period of the
camera 30, the real defects generated in the liquid crystal display
panel can be accurately detected.
[0066] It will be apparent to those skilled in the art that various
modification and variations can be made in the present invention.
Thus, it is intended that the present invention covers the
modifications and variations of this invention provided they come
within the scope of the appended claims and their equivalents.
* * * * *